Ensure the right perl is used for TAP tests on msys

In particular, perl with $Config{osname} = msys should only be used if
the build target is msys (which is currently buildable but not usable).
For builds targeted at native Windows, perl from the ucrt64 toolchain is
suitable.

Discussion: https://postgr.es/m/20220216210141.5glt5isg5qtwty4c@alap3.anarazel.de

config/check_modules.pl

@@ -6,6 +6,7 @@
 #
 use strict;
 use warnings;
+use Config;
 
 use IPC::Run 0.79;
 
@@ -19,5 +20,9 @@ diag("IPC::Run::VERSION: $IPC::Run::VERSION");
 diag("Test::More::VERSION: $Test::More::VERSION");
 diag("Time::HiRes::VERSION: $Time::HiRes::VERSION");
 
+# Check that if prove is using msys perl it is for an msys target
+ok(($ENV{__CONFIG_HOST_OS__} || "") eq 'msys',
+   "Msys perl used for correct target")
+  if $Config{osname} eq 'msys';
 ok(1);
 done_testing();

configure

@@ -19758,6 +19758,7 @@ fi
   # installation than perl, eg on MSys, so we have to check using prove.
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for Perl modules required for TAP tests" >&5
 $as_echo_n "checking for Perl modules required for TAP tests... " >&6; }
+  __CONFIG_HOST_OS__=$host_os; export __CONFIG_HOST_OS__
   modulestderr=`"$PROVE" "$srcdir/config/check_modules.pl" 2>&1 >/dev/null`
   if test $? -eq 0; then
     # log the module version details, but don't show them interactively

configure.ac

@@ -2432,6 +2432,7 @@ if test "$enable_tap_tests" = yes; then
   # AX_PROG_PERL_MODULES here, but prove might be part of a different Perl
   # installation than perl, eg on MSys, so we have to check using prove.
   AC_MSG_CHECKING(for Perl modules required for TAP tests)
+  __CONFIG_HOST_OS__=$host_os; export __CONFIG_HOST_OS__
   [modulestderr=`"$PROVE" "$srcdir/config/check_modules.pl" 2>&1 >/dev/null`]
   if test $? -eq 0; then
     # log the module version details, but don't show them interactively